Method, control device and computer program for determining a moisture content in a fuel cell system, gas mixture analysis device and fuel cell system

Abstract

The present invention relates to a method, a control device (160) and a computer program for determining a moisture content in a gas mixture present in an anode conducting system (130) of a fuel cell system (100), and to a gas mixture analysis device (180) and a fuel cell system (100). The anode conducting system (130) fluidically connects a hydrogen injector (122) to an anode of the fuel cell system (100) and has at least one thermal conductivity sensor (131, 133), which is designed to generate a gas signal which is representative of the thermal conductivity in the gas mixture. The method according to the invention comprises receiving a first gas signal from the at least one thermal conductivity sensor (131, 133) at a first time (t1), transmitting a hydrogen supply signal, which indicates a predefined hydrogen supply rate, to the hydrogen injector (122) at a second time (t2), receiving a second gas signal from the at least one thermal conductivity sensor (131, 133) at a fourth time (t4), at which hydrogen is supplied to the anode conducting system (130), and determining the moisture content in the anode conducting system (130) at least partially based on the first gas signal, the second gas signal and the predefined hydrogen supply rate.

Description

[0001] Description

[0002] Method, control device and computer program for determining a moisture content in a fuel cell system as well as gas mixture analysis device and fuel cell system

[0003] The present invention relates to a method, a control device and a computer program for determining a moisture content in a fuel cell system, in particular in a gas mixture present in an anode line system of the fuel cell system, by means of a thermal conductivity sensor, as well as a gas mixture analysis device and a fuel cell system.

[0004] Fuel cell systems are powered by hydrogen from a hydrogen tank. To measure the hydrogen concentration in the fuel cell system, it is known to use thermal conductivity sensors. These sensors generate a gas signal representative of the sum of the moisture content, nitrogen concentration, and hydrogen concentration at the respective measuring point in the fuel cell system. State-of-the-art thermal conductivity sensors are based on the thermal conductivity measurement principle. The thermal conductivity of the entire gas mixture is determined, from which the concentration of a gas component of the gas mixture can be derived. In particular, the hydrogen concentration in the gas mixture, for example, can be derived, since the thermal conductivity of hydrogen is significantly greater than the thermal conductivity of many other gas components.

[0005] However, the known thermal conductivity sensors are cross-sensitive to water (vapor), so that the gas signal from the thermal conductivity sensor indicates the sum of the moisture content and the hydrogen concentration (and, if present in the gas mixture, the nitrogen concentration). Thus, the moisture present in the fuel cell system distorts the measurement of the hydrogen concentration. Examples of known prior art include DE 10 2016 210 518 A1, US 2019 / 0288314 A1, DE 102020 211 893 A1, DE 102020 117 820 A1, and US 2006 Z 0 169 024 A1.

[0006] The present invention is essentially based on the object of determining the moisture content in the anode line system of a fuel cell system as accurately as possible.

[0007] This object is achieved with a method according to independent claim 1, a control device according to claim 8, a gas mixture analysis device according to claim 11, a fuel cell system according to claim 12, a computer program according to claim 14 and a computer program product according to claim 15. Advantageous embodiments are specified in the subclaims.

[0008] The present invention is essentially based on the idea of ​​exploiting the cross-sensitivity of a thermal conductivity sensor arranged in an anode line system of a fuel cell system to moisture in the anode line system to determine the moisture content in the gas mixture present in the anode line system based on the gas signals of the thermal conductivity sensor. Furthermore, the present invention is essentially based on the idea of ​​compensating the gas signal of the thermal conductivity sensor, which is designed to detect the thermal conductivity of the gas mixture, for the moisture content, based on knowledge of the determined moisture content, thus enabling a more precise determination of the hydrogen concentration in the gas mixture.

[0009] The present invention is also essentially based on the fact that the first gas signal is representative of the thermal conductivity of the gas mixture present in the anode line system before the injection of fresh hydrogen, and the second gas signal is representative of the thermal conductivity of the gas mixture present in the anode line system during or after the injection of fresh hydrogen. The first and second gas signals can be generated either by means of a thermal conductivity sensor at the same measuring point at two different times or by means of two thermal conductivity sensors at two different measuring points at essentially the same time, wherein one of the two measuring points is located at a position to which fresh hydrogen is or was supplied, and the other measuring point is located at a position at which the freshly supplied hydrogen is not (yet) present.

[0010] Accordingly, according to a first aspect of the present invention, a method for determining a moisture content in a gas mixture present in an anode line system of a fuel cell system is disclosed. The anode line system fluidly connects a hydrogen injector, which is configured to supply hydrogen from a hydrogen tank into the anode line system, to an anode of the fuel cell system. The anode line system has at least one thermal conductivity sensor, which is configured to generate a gas signal representative of the thermal conductivity of the gas mixture in the anode line system. The method according to the invention comprises receiving a first gas signal from the at least one thermal conductivity sensor at a first time and transmitting a hydrogen supply signal to the hydrogen injector at a second time.The hydrogen supply signal causes the hydrogen injector to supply hydrogen from the hydrogen tank to the anode line system at a predetermined hydrogen supply rate between the second time and a third time. The method according to the invention further comprises receiving a second gas signal from the at least one thermal conductivity sensor at a fourth time at which the hydrogen from the hydrogen tank is being or has been supplied to the anode line system, and determining the moisture content in the anode line system based at least partially on the first gas signal, at least partially on the second gas signal, and at least partially on the predetermined hydrogen supply rate. According to the invention, the moisture content in the gas mixture can be determined by processing the first gas signal, the second gas signal, and the predetermined hydrogen supply rate.

[0011] Preferably, the first point in time is before or equal to the second point in time.

[0012] In an advantageous embodiment of the method according to the invention, the fourth point in time is after the second point in time and before the third point in time or is equal to the third point in time.

[0013] In a preferred embodiment of the method according to the invention, the second gas signal is representative of the thermal conductivity of the gas mixture at a position immediately downstream of the hydrogen injector. In particular, the second gas signal can be representative of the sum of the moisture content, the hydrogen concentration, and the nitrogen concentration in the gas mixture in the anode line system.

[0014] In a further preferred embodiment of the method according to the invention, the first gas signal is representative of the thermal conductivity of the gas mixture at a position downstream of the anode. In particular, the first gas signal can be representative of the sum of the moisture content, the hydrogen concentration, and the nitrogen concentration in the gas mixture in the anode line system.

[0015] In an advantageous embodiment, the method according to the invention further comprises receiving a third gas signal from the at least one thermal conductivity sensor at a fifth point in time, which is chronologically after the third and fourth points in time, and determining the hydrogen concentration at least partially based on the determined moisture content and at least partially based on the third gas signal received at the fifth point in time. In a particularly preferred embodiment of the method according to the invention, the anode line system has a recirculation pump designed to circulate the gas mixture flowing through the anode line system at a predetermined circulation rate such that the gas mixture is repeatedly supplied to the anode. The method according to the invention further comprises determining a rate ratio between the circulation rate of the recirculation pump and the hydrogen supply rate of the hydrogen injector.The determination of the moisture content in the anode line system is also based at least partly on the determined rate ratio.

[0016] According to a further aspect of the present invention, a control device is disclosed which is designed to carry out the steps of a method according to the invention.

[0017] In an advantageous embodiment, the control device according to the invention comprises a first control device section for carrying out the step of receiving the first and second gas signals from the at least one thermal conductivity sensor, a second control device section for carrying out the step of sending a hydrogen supply signal to the hydrogen injector, and a third control device section for carrying out the step of determining the moisture content in the anode line system.

[0018] In a further advantageous embodiment, the control device according to the invention further comprises a fourth control device section for carrying out the step of determining the hydrogen concentration.

[0019] According to yet another aspect of the present invention, a gas mixture analysis device for a fuel cell system is disclosed. The gas mixture analysis device according to the invention comprises at least one thermal conductivity sensor configured to generate the gas signal, and a control device according to the invention.In a preferred embodiment of the gas mixture analysis device according to the invention, a first thermal conductivity sensor is designed to generate the second gas signal, which is representative of the thermal conductivity of the gas mixture present in the anode line system of a fuel cell system downstream of the hydrogen injector, and a second thermal conductivity sensor is designed to generate the first gas signal, which is representative of the thermal conductivity of the gas mixture present in the anode line system of a fuel cell system downstream of the anode and upstream of the hydrogen injector.

[0020] According to yet another aspect of the present invention, a fuel cell system is disclosed comprising an anode, an anode conduit system fluidly connecting a hydrogen injector configured to supply hydrogen from a hydrogen tank into the anode conduit system to the anode, and a gas mixture analysis device according to the invention.

[0021] According to yet another aspect of the present invention, a computer program is disclosed comprising instructions which, when executed by a computing unit, cause the computing unit to carry out a method according to the invention.

[0022] According to yet another aspect of the present invention, a computer-readable medium is disclosed on which the computer program according to the invention is stored.

[0023] Further advantages and features of the present invention will become apparent to those skilled in the art by practicing the teachings described herein and viewing the accompanying single drawings in which:

[0024] Fig. 1 is a schematic representation of an inventive

[0025] Fuel cell system for a vehicle, Fig. 2 shows an exemplary diagram in which an exemplary time course of a gas signal of a thermal conductivity sensor of the fuel cell system of Fig. 1 is entered, and

[0026] Fig. 3 shows an exemplary flow diagram of a method according to the invention for determining a moisture content in the gas mixture present in the anode line system of the fuel cell system of Fig. 1.

[0027] In the context of the present disclosure, the term "gas mixture" describes a mixture of hydrogen and other gaseous components, such as moisture in the form of water vapor and / or an inert gas, e.g., argon, or other gases, such as nitrogen. In particular, the term "gas mixture" in an anode line system of a fuel cell system describes a mixture of the components hydrogen, water (vapor), and nitrogen.

[0028] In the context of this disclosure, the term "signal" describes raw data that is converted into a form that can be sent over the selected transport medium for data transmission. This can be done analogically or digitally, with the data first being sampled and converted into discrete (often binary-coded) values, which are then sent over the medium as current pulses or voltages of varying magnitudes. Furthermore, in the context of this disclosure, the signals are transmitted and received continuously. For example, digital signals are transmitted and received at intervals of a few milliseconds.

[0029] In the context of the present disclosure, the term “moisture content” describes the concentration (in percent [%]) of water (vapor) in the gas mixture within the anode line system. This can be the relative or absolute humidity in the gas mixture. Fig. 1 shows a schematic representation of a fuel cell system 100 according to the invention for a vehicle. The fuel cell system 100 comprises a fuel cell 110, such as a fuel cell stack. The fuel cell 110 comprises, as is known from the prior art, an anode and a cathode separated from one another by a membrane. For example, the fuel cell 110 can be a so-called PEM fuel cell, in which the membrane is a proton exchange membrane through which the protons formed at the anode can pass to the cathode.

[0030] The fuel cell system 100 further comprises a hydrogen tank 120 in which essentially pure hydrogen is stored, preferably under pressure. The hydrogen tank 120 may have valves (not explicitly shown in Fig. 1) with which the flow of hydrogen into and out of the hydrogen tank 120 can be controlled.

[0031] The fuel cell system 100 of Fig. 1 further comprises an anode line system 130, which is designed to supply the hydrogen flowing out of the hydrogen tank 120 to the anode of the fuel cell 110 and to divert or recirculate the gas mixture flowing past the anode. For this purpose, the anode line system 130 comprises an anode supply line 132, which is fluidly connected to a hydrogen injector 122, which in turn is designed to inject hydrogen from the hydrogen tank 120 into the anode line system 130, in particular into the anode supply line 132. The anode supply line 132 is fluidly connected to an anode line 134, which supplies the gas mixture to the anode of the fuel cell 110. The anode line system 130 further comprises an anode discharge line 136, which is fluidly connected to the anode line 134 and can discharge the gas mixture flowing through the anode line 134 and supply it to an exhaust gas line (not explicitly shown in Fig. 1).The anode line system 130 further comprises an anode return line 138 which fluidly connects the anode discharge line 136 to the anode supply line 132 and in which a return pump 139 is arranged which is designed to return the anode discharge line 136 to the anode supply line 132.

[0032] The gas mixture flowing through the anode discharge line 136 is returned to the anode supply line 132 at a predetermined circulation rate (in liters per second [l / s]). The circulation rate can be adjusted and set, for example, by the control signals of the recirculation pump 139. Consequently, a circuit is formed between the anode supply line 132, the anode line 134, the anode discharge line 136, and the anode return line 138, in which the gas mixture can be circulated and recirculated by the recirculation pump 139.

[0033] Upon receiving a corresponding hydrogen supply signal, the hydrogen injector 122 can inject hydrogen from the hydrogen tank 120 into the anode line system 130 at a predetermined hydrogen supply rate. The hydrogen supply rate (in liters per second [l / s]) can be determined and / or adjusted, for example, based on the pressure in the hydrogen tank 120, the temperature of the hydrogen in the hydrogen tank, the opening cross-section of the hydrogen injector 122, the pulse duration, the injection frequency, and / or the injection frequency.

[0034] The anode line system 130 further includes a purge valve 137, which is arranged in the anode discharge line 136 downstream of the outlet point of the anode return line 138 and is designed to open or close the anode discharge line 136. During normal operation of the fuel cell 110, the purge valve 137 is closed, so that the just-described circulation and recirculation process of the gas mixture can be provided by the return pump 139.

[0035] Furthermore, the anode line system 130 has a thermal conductivity sensor (also called a hydrogen sensor) 131, which is arranged in the anode feed line 132 downstream of the hydrogen injector 122 and is designed to generate a gas signal that is representative of the thermal conductivity of the gas mixture in the anode line system 130, in particular in the anode feed line 132 immediately downstream of the hydrogen injector 122. Due to the cross-sensitivity of the thermal conductivity sensor 131 to the moisture in the gas mixture, the gas signal is also representative of the sum of the moisture content, hydrogen concentration, and nitrogen concentration in the gas mixture within the anode line system 130, in particular within the anode feed line 132. The thermal conductivity sensor 131 can be a gas sensor based on the thermal conductivity principle. The gas signals of the thermal conductivity sensor 131 are preferably digital signals orData that can be processed by a data processing device, which may include a processor and a memory.

[0036] The fuel cell system 100 further comprises a cathode line system 140 consisting of a cathode supply line 142, a cathode line 144 connected to the cathode, and a cathode discharge line 146. Furthermore, the cathode line system 140 comprises a cathode bypass 148, which fluidically connects the cathode supply line 142 to the cathode discharge line 146 and in which a bypass valve 149 is arranged for blocking or opening the cathode bypass line 148. The cathode discharge line 146 can divert the air supplied to the cathode via the cathode supply line 142 into the exhaust system. A pressure sensor 141 for detecting the pressure in the cathode supply line 142 and a cathode inlet valve 145, which can be a throttle valve, for example, can be arranged in the cathode supply line 142.Similarly, the cathode discharge line 146 may include a cathode outlet valve 147 and a pressure sensor 143 disposed downstream of the cathode discharge line 146 for detecting the pressure in the cathode discharge line 146. Furthermore, a compressor 170 for compressing the air, a water separator 172, and a throttle valve 174 are disposed in the cathode line system 140.

[0037] The fuel cell system 100 of Fig. 1 further comprises an on-board power supply branch 150 that includes electrical consumers. In particular, the on-board power supply branch 150 describes at least part of an electrical system that can store and distribute the electrical energy generated by the fuel cell 110.

[0038] From Fig. 1, it is further apparent that a control device 160 is provided, which can be connected to all components of the fuel cell system 100. Although no separate lines are shown for this purpose in Fig. 1, such electrical connecting lines can be present in the form of connecting lines or wireless communication devices. The control device 160 can have a plurality of control device sections, such as a first control device section 162, a second control device section 164, a third control device section 166, a fourth control device section 168, and a fifth control device section 169, which will be discussed in more detail below with reference to Fig. 3.

[0039] The control device 160 may include a processor and a memory. Alternatively, the control device 160 may be the processor coupled to the memory. The processor may be a central processing unit (CPU). The processor may further be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or another programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor or the like.

[0040] Memory includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), or portable read-only memory (e.g., CD-ROM). The memory is configured to store associated program instructions and associated data.

[0041] Optionally, the anode line system 130 can have a further thermal conductivity sensor 133 which, as shown in Fig. 1, can be arranged in the anode return line 138 and can be designed to generate a gas signal which is representative of the thermal conductivity of the gas mixture in the anode line system 130, in particular in the anode return line 138 downstream of the anode and upstream of the hydrogen injector 122. Due to the cross-sensitivity of the thermal conductivity sensor 133 to the moisture in the gas mixture, the gas signal of the further thermal conductivity sensor 133 is also representative of the sum of the moisture content, hydrogen concentration and nitrogen concentration in the gas mixture at a position downstream of the anode, in particular in the anode return line 132. The gas signals of the thermal conductivity sensor 132 are preferably digital signals orData that can be processed by a data processing device, which may include a processor and a memory.

[0042] The thermal conductivity sensor 131, together with the control device 160, forms a gas mixture analysis device 180 (see dashed box in Fig. 1 ) for the fuel cell system 100. The gas mixture analysis device 180 can optionally have the further thermal conductivity sensor 133.

[0043] Fig. 2 shows an exemplary diagram in which an exemplary temporal profile of a gas signal 200 of the thermal conductivity sensor 131 of the fuel cell system of Fig. 1 is plotted. Time t is plotted on the abscissa, and the gas signal, which is representative of the thermal conductivity L of the mixture at the measuring point, is plotted on the ordinate.

[0044] The gas mixture in the anode line system 130 consists of hydrogen, water (vapor) or moisture, and nitrogen. Since the thermal conductivity of hydrogen is significantly greater than that of the other components, water (vapor) and nitrogen, the thermal conductivity of the gas mixture is essentially influenced by the hydrogen concentration. In Fig. 2, at time t1, at which the fuel cell system 100 is in normal operating mode, a first gas signal is generated by the thermal conductivity sensor 131. At time t2, a hydrogen supply signal can be sent to the hydrogen injector 122 by the control device 160, which causes the hydrogen injector 122 to inject hydrogen from the hydrogen tank 120 into the anode line system 130 at a predetermined hydrogen supply rate.At time t3, a second gas signal is generated by the thermal conductivity sensor 131. At time t4, the injection of hydrogen into the anode line system 130 by the hydrogen injector 122 is terminated. At time t5, at which the fuel cell system 100 is back in normal operating mode, a third gas signal is generated by the thermal conductivity sensor 131, from which the hydrogen concentration is to be derived.

[0045] In the following, an exemplary embodiment of a method according to the invention for determining the moisture content in the gas mixture present in the anode line system 130 of the fuel cell system 100 of FIG. 1 and for determining a corrected hydrogen signal that is representative of the hydrogen concentration in the gas mixture present in the anode line system 130 of the fuel cell system 100 of FIG. 1 is described with reference to the flow diagram shown in FIG. 3.

[0046] The method of Fig. 3 starts at step 300 and then proceeds to step 310, at which, during normal operation of the fuel cell system 100 of Fig. 1, the control device 160, in particular the first control device section 162, receives a (digital) first gas signal from the thermal conductivity sensor 131, which is representative of the thermal conductivity of the gas mixture in the anode line system 130, in particular in the anode feed line 132. The first gas signal is received from the thermal conductivity sensor 131 at the first time t1 (see Fig. 2). During normal operation of the fuel cell system 100, the purge valve 137 is in a closed position, meaning that no gas mixture can flow out of the anode line system 130 through the purge valve 137.At the same time, during normal operation of the fuel cell system 100, the recirculation pump 139 is in an activated state so that the gas mixture present in the anode line system 130 can flow by means of the recirculation pump 139 through the circuit formed by the anode supply line 132, the anode line 134, the anode discharge line 136 and the return line 138 at a predetermined circulation rate.

[0047] During operation of the fuel cell system 100, the hydrogen injector 122 is deactivated and does not inject any (fresh) hydrogen into the anode line system 130. The gas mixture in the anode line system 130 comprises hydrogen, nitrogen, and water (vapor). The water (vapor) content can be referred to as the moisture content. The proportions or concentrations or contents of the respective components of the gas mixture in the anode line system are location-specific and vary due to the conversion of the hydrogen at the anode. Consequently, due to the conversion of the hydrogen at the anode, the hydrogen concentration in the gas mixture decreases, which is why the thermal conductivity of the gas mixture also decreases (see the essentially decreasing curve of the gas signal 200 in Fig. 2 before the first time t1).

[0048] In a subsequent step 320, if necessary, the control device 160, in particular the second control device section 164, sends a hydrogen supply signal to the hydrogen injector 122. The hydrogen supply signal is designed to cause the hydrogen injector 122 to inject hydrogen from the hydrogen tank 120 into the anode line system 130, in particular into the anode supply line 132, at a predetermined hydrogen supply rate. The injection process of hydrogen from the hydrogen tank 120 into the anode line system 130 begins at the second time t2 and lasts until the third time t3. Preferably, the first time t1 and the second time t2 are the same.Due to the injection of hydrogen into the anode line system 130, the hydrogen concentration in the gas mixture at the measuring point of the thermal conductivity sensor 131 increases significantly, which is why the thermal conductivity of the gas mixture also increases significantly (see the course of the gas signal 200 in Fig. 2 shortly after the second time t2). After this increase, the gas signal remains essentially constant during the hydrogen injection process, since the hydrogen concentration settles at an essentially constant value due to the essentially constant circulation rate of the recirculation pump 139 and the essentially constant hydrogen supply rate of the hydrogen injector 122.

[0049] In a subsequent step 330, the control device 160, in particular the first control device section 162, receives a second gas signal from the thermal conductivity sensor 131. The second gas signal is received at the fourth time t-4, which preferably occurs during the injection process of the hydrogen from the hydrogen tank 120. Alternatively, the fourth time t4 and the third time t3 can coincide. In a further alternative embodiment, the fourth time t4 can immediately follow the third time t3, whereby it must be ensured that injected hydrogen still reaches the measuring point.

[0050] In a subsequent step 340, the control device 160, in particular the third control device section 166, can determine the moisture content in the anode line system 130, in particular in the anode supply line 132, based at least partially on the first gas signal received at the first time t1, at least partially on the second gas signal received at the fourth time t4, and at least partially on the predetermined hydrogen supply rate. In a preferred embodiment, the circulation rate of the recirculation pump 139 can also be taken into account. The present invention takes advantage of the fact that, due to the injection process of hydrogen into the anode line system 130, the gas signal 200 increases between times t2 and t3 and remains constant at least in sections during the injection (see gas signal 200 between times t2 and t3 in Fig. 2).For example, if before injection the gas mixture in the anode feed line 132 consists of approximately 80% hydrogen, approximately 10% nitrogen and approximately 10% moisture content and flows at a circulation rate of 5 l / s in the anode line system 130 and then hydrogen is injected by means of the hydrogen injector 122 at a hydrogen feed rate of 5 l / s, the thermal conductivity t of the gas mixture increases significantly (see rising profile of the gas signal 200 in Fig. 2 immediately after the second time t2).

[0051] In particular, it is desirable to have a gas mixture with a high humidity in the anode line system 130. This means that the gas mixture should contain moist hydrogen, such as 100% hydrogen with a relative humidity of 70%. Depending on the temperature and pressure, this can be expressed, for example, in moles with an 80% hydrogen concentration and a 20% humidity content (with 0% nitrogen). The hydrogen concentration of 80% can then be determined from the thermal conductivity of this gas mixture, determined by the thermal conductivity sensor 131.

[0052] However, if a "dry" gas mixture were present in the anode line system 130, for example, a gas mixture consisting of 80% hydrogen, 20% nitrogen, and 0% moisture, a hydrogen concentration of 80% could also be determined using the thermal conductivity sensor 131. This means that the hydrogen concentration of 80% and a residual mixture concentration (moisture and nitrogen) of 20% can be determined using the thermal conductivity sensor 131. However, the system conditions for a gas mixture of 80% hydrogen and 20% moisture are different than for a gas mixture of 80% hydrogen and 20% nitrogen. According to the invention, the moisture content of the gas mixture can be determined using the two gas signals and the predetermined hydrogen supply rate, applying known thermodynamic relationships.

[0053] The method of Fig. 3 may then proceed to a step 350 at which the control device 160, in particular the fourth control device section 168, sends a moisture signal that is representative of the moisture content determined in step 340.

[0054] In a further step 360, the control device 160, in particular again the first control device section 162, can receive a third gas signal from the thermal conductivity sensor 131 at the fifth time t5, at which the fuel cell system 100 is again in the normal operating mode and no injection of hydrogen into the anode line system 130 takes place.

[0055] In a subsequent step 370, the control device 160, in particular the fourth control device section 169, can determine the hydrogen concentration in the anode line system 130 based at least partially on the moisture content determined in step 340 and at least partially on the third gas signal received in step 360. In particular, the third gas signal can be adjusted for moisture content, thus determining the actual hydrogen concentration. The determined moisture content can be used as a control variable for the operation of the fuel cell system, thereby enabling the fuel cell system to achieve a longer service life.

[0056] In a subsequent step 380, the control device 160, in particular the fourth control device section 168, can send a hydrogen signal that is representative of the hydrogen concentration determined in step 370 before the method ends at step 390.

[0057] In an alternative embodiment, where the optional thermal

[0058] Conductivity sensor 133 (see Fig. 1 ) is present, step 310 can take place after step 320 simultaneously with step 330 at a sixth time t6 (see Fig. 2), which is immediately after the second time t2. In this case, the control device 160, in particular the first control device section 162, receives the second gas signal from the thermal conductivity sensor 131 and the first gas signal from the thermal conductivity sensor 133. In particular, at the sixth time t6, it can be assumed that the thermal conductivity sensor 131 is already measuring the gas mixture into which (fresh) hydrogen from the hydrogen tank 120 is currently being injected, whereas the thermal conductivity sensor 133 is measuring the gas mixture in which the injected hydrogen is not yet contained.

[0059] In such an alternative embodiment, the gas signals of the two thermal conductivity sensors can then be mutually checked for plausibility and corrected during normal operation of the fuel cell system 100.

[0060] In a preferred embodiment, in step 340, a rate ratio between the circulation rate of the recirculation pump 139 and the predetermined hydrogen supply rate of the hydrogen injector 122 is also determined. In addition, in step 340, the determined rate ratio can additionally be taken into account when determining the moisture content.

[0061] With the present invention, it is thus possible to determine the moisture content in the gas mixture present in the anode line system 130 and, during further operation of the fuel cell system, to clean the gas signal of the thermal conductivity sensor 131 of the moisture content so that the actual hydrogen concentration in the anode line system 130 can be determined as accurately as possible.

Claims

Patent claims 1. A method for determining a moisture content in a gas mixture present in an anode line system (130) of a fuel cell system (100), wherein the anode line system (130) fluidly connects a hydrogen injector (122), which is designed to supply hydrogen from a hydrogen tank (120) into the anode line system (130), to an anode of the fuel cell system (100), wherein the anode line system (130) has at least one thermal conductivity sensor (131, 133) which is designed to generate a gas signal which is representative of the thermal conductivity of the gas mixture in the anode line system (130), wherein the gas mixture consists of hydrogen, nitrogen and wherein the method comprises: Receiving a first gas signal from the at least one thermal conductivity sensor (131, 133) at a first time (t1), Sending a hydrogen supply signal to the hydrogen injector (122) at a second time (t2), wherein the hydrogen supply signal causes the hydrogen injector (122) to supply hydrogen from the hydrogen tank to the anode line system (130) at a predetermined hydrogen supply rate between the second time (t2) and a third time (t3), receiving a second gas signal from the at least one thermal conductivity sensor (131, 133) at a fourth time (t4) at which the hydrogen from the hydrogen tank (120) is or has been supplied to the anode line system (130), and Determining the moisture content in the anode line system (130) at least partially based on the first gas signal, at least partially based on the second gas signal, and at least partially based on the predetermined hydrogen supply rate.

2. The method according to claim 1, wherein the first time (t1) is before or equal to the second time (t2).

3. Method according to one of the preceding claims, wherein the fourth time (t4) is after the second time (t2) and before the third time (t3) or is equal to the third time (t3).

4. The method according to any one of the preceding claims, wherein the second gas signal is representative of the thermal conductivity of the gas mixture at a position immediately downstream of the hydrogen injector (122).

5. A method according to any one of the preceding claims, wherein the first gas signal is representative of the thermal conductivity of the gas mixture at a position downstream of the anode.

6. The method according to any one of the preceding claims, further comprising: receiving a third gas signal from the at least one thermal conductivity sensor at a fifth time (t5) which is later than the third and fourth time (t3, t4), and Determining the hydrogen concentration based at least in part on the determined moisture content and at least in part on the third gas signal received at the fifth time (t5).

7. The method according to any one of the preceding claims, wherein the anode line system (130) comprises a recirculation pump (139) configured to circulate the gas mixture flowing through the anode line system (130) at a predetermined circulation rate such that the gas mixture is repeatedly supplied to the anode, the method comprising: Determining a rate ratio between the circulation rate of the recirculation pump (139) and the predetermined hydrogen supply rate of the hydrogen injector (122), wherein the determination of the moisture content in the anode conduit system (130) is further based at least in part on the determined rate ratio.

8. Control device (160) designed to carry out the steps of the method according to one of the preceding claims.

9. Control device (160) according to claim 8, comprising: a first control device section (162) for Carrying out the step of receiving the first and second gas signals from the at least one thermal conductivity sensor (131, 133), a second control device section (164) for carrying out the step of sending a hydrogen supply signal to the hydrogen injector (122), and a third control device section (166) for carrying out the step of determining the moisture content in the anode line system (130).

10. The control device (160) according to any one of claims 8 and 9, further comprising: a fourth control device portion (168) for performing the step of determining the hydrogen concentration.

11. A gas mixture analysis device (180) for a fuel cell system (100), comprising: at least one thermal conductivity sensor (131, 133) configured to generate gas signals, and a control device (160) according to any one of claims 8 to 10.

12. Gas mixture analysis device (180) according to claim 11, wherein a first thermal conductivity sensor (131) is designed to generate the second gas signal, which is representative of the thermal conductivity of the gas mixture present in the anode line system (130) of a fuel cell system (100) downstream of the hydrogen injector, wherein a second thermal conductivity sensor (133) is designed to generate the first gas signal, which is representative of the thermal conductivity of the gas mixture present in the anode line system (130) of a Fuel cell system (100) existing gas mixture downstream of the anode.

13. A fuel cell system (100), comprising: - an anode, an anode line system (130) fluidly connecting a hydrogen injector (122) configured to supply hydrogen from a hydrogen tank (120) into the anode line system (130) to the anode, and a gas mixture analysis device (180) according to one of claims 11 and 12.

14. A computer program comprising instructions which, when executed by a computing unit, cause the computing unit to carry out a method according to any one of claims 1 to 7. 15 A computer-readable medium on which the computer program according to claim 14 is stored.

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